It was at the Trident Conference, held in Washington in May 1943, that the Allies, who had already been conducting operations in the Mediterranean for several months, adopted the principle of a landing on the western coast of Europe. The date they initially set was May 1944. Three months after the conference, the beaches of Lower Normandy were chosen in preference to those of the Pas-de-Calais.
In December 1943, General Eisenhower took up his post as Supreme Commander of the operation, codenamed Overlord. He was assisted by General Montgomery, placed at the head of the land forces. When the two men examined the plans drawn up by COSSAC (the headquartersond by Major-General Morgan, in charge of preparing the operations), they concluded that the proposed landing zone, between Grandcamp and Courseulles, was too narrow. They therefore decided to add two extra beaches: one further east, between Courseulles and the Orne estuary, the other further west, on the Cotentin coast, with a view to capturing the port of Cherbourg more rapidly. As this alteration meant that extra resources would be required, notably aircraft and transport and assault barges, D-Day was postponed for a month, until June 1944.
It was now a question of deciding on the precise date and time of the assault. There were a number of parameters to be considered. Predicting that the Allies would attack at high tide, Rommel had covered the beaches with large numbers of obstacles. The assault would therefore have to take place at the rising half tide, to prevent the barges from being impaled on the traps. The airborne troops needed a full moon to carry out their mission, while the navy, which had to bombard the German defences forty-five minutes before H-Hour, wanted to operate at first light, in order to pinpoint its targets more accurately. These three conditions (half tide, at dawn, preceded by a night with a full moon) only prevailed a few days each month. Eisenhower therefore fixed the launch of operations for June 5th, with the possibility of postponing them until the 6th or 7th.
In the event, bad weather in the Channel at the beginning of June forced Eisenhower to put the landings off until the next day, when the weather reports predicted that there would be a brief lull.
And that is how Tuesday June 6th 1944 entered the history books!